Apparatus for recharging pressurized balls and method

ABSTRACT

An apparatus, system and method for recharging depleted pressurized balls that uses pressurized gas is disclosed. A pressure vessel includes a cylindrical shell with a closed end and a spaced apart and opening top connected by a wall to form a charging chamber. The vessel may be pivotally secured to a base. A port in the outer wall, closed end, or top of the vessel permits gas entry and exit for charging. The chamber is filled with an appropriate number of discharged balls and then is sealed and charged with high pressure gas having a molecular weight heavier than air. The chamber is monitored to determine when the balls have reached a desired internal pressure. Once the balls reach the desired internal pressure they are removed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and is a continuation-in-part of currently pending PCT Application PCT/US2010/059399, filed on Dec. 8, 2010, and currently pending U.S. application Ser. No. 12/657,032 filed Jan. 12, 2010, which is a continuation-in-part of U.S. application Ser. No. 11/820,423, filed Jun. 19, 2007, now issued as U.S. Pat. No. 7,658,211.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the field of recharging depleted or exhausted or dead or depressurized balls that are used in sporting events. In particular, the present invention relates to an apparatus and method for recharging depleted or exhausted or dead or depressurized balls to restore the liveliness and optimum configuration of the individual balls.

2. Description of the Known Art

Many games use a gas pressurized hollow ball during play (i.e. football, basketball, soccer, tennis, etc.). The apparatus and method according to the invention is suitable for use with any such pressurized ball. However, as an aid to the reader the background and detailed description sections of this document will focus on tennis balls and padel balls (padel ball is a game that is similar to tennis and uses a similar type of ball). This narrative convenience should not be interpreted as limiting the scope of the invention.

In the game of tennis, the ball is spherical, has a standard diameter and is covered with a fibrous nap. Important parameters of the tennis ball are its bounce or liveliness or resiliency and this is a function of the ball's internal gas pressure, its size and spherical configuration and the condition of the fibrous nap. All of these parameters should be maintained constant and uniform from ball to ball and during the useful life of the ball. Since the reaction of the ball to the impact of the racket and its ground rebound characteristics are functions of the above parameters, any significant change or variation thereof adversely affects the proper playing of the game.

As is well known, the resiliency exhibited by tennis balls is due, at least in part, to the pressurization of the tennis balls during manufacturing. To be suitable for tournament play, tennis balls must be able to meet quite rigid specifications regarding their size, the distance to which they rebound when dropped from a standard height, the amount of deformation they exhibit under an applied standard force, and their surface characteristics.

For example, current International Tennis Federation (ITF) rules require that tennis balls weigh between 56.0-59.4 grams. All manufacturers strive to comply with these rigid specifications to insure that the balls they manufacture exhibit the uniformity demanded by serious amateur as well as professional tennis competitors.

Tennis balls are generally packaged and marketed in pressurized hermetically sealed containers to minimize or prevent any outwardly diffusion of the pressurized gas in the ball which would reduce its liveliness and to prevent distortion of the ball from its standard size or shape as a consequence of the ball's high internal pressure. A basic problem with tennis balls presently in use is that, as the balls age, they lose pressure. This pressure loss results from the diffusion of whatever gas may be used to inflate tennis balls during manufacture through the tennis ball surface and out into the atmosphere. Partially to combat this loss of pressure, tennis balls are sold in pressurized canisters that generally contain three or four tennis balls. Once the canister is opened, the tennis balls are removed from their pressurized environment and, as a result of the internal to external pressure differential they begin to deflate and distort thus limiting the useful life of the ball.

As stated previously, with usage and/or the passage of time, the internal pressurization of tennis balls eventually escapes until the internal pressure of the tennis balls drops to atmospheric pressure. At that time, the unpressurized and depleted tennis balls are considered to be dead or flat even though the tennis balls may otherwise be acceptable. Depleted tennis balls are typically discarded. While many of the tennis balls may be retired because their surfaces have become worn beyond acceptable limits, many more tennis balls are retired simply because they have lost their pressurization. Discarding depleted but otherwise acceptable tennis balls can be extremely wasteful, particularly at large tennis clubs and country clubs or tennis instruction academies where the quantity of depleted tennis balls can be high.

Others have proposed solutions to deal with depleted tennis balls, including recharging and/or recycling apparatus and methods. Patents disclosing information relevant to tennis ball pressurization include U.S. Pat. No. 4,124,117 issued to Rudy on Nov. 7, 1978; U.S. Pat. No. 1,207,813 issued to Stockton on Dec. 12, 1916; U.S. Pat. No. 4,019,629 issued to Dubner et al. on Apr. 26, 1977; U.S. Pat. No. 4,020,948 issued to Won on May 3, 1977; U.S. Pat. No. 4,046,491 issued to Roeder on Sep. 6, 1977; U.S. Pat. No. 4,073,120 issued to Berggren on Feb. 14, 1978; U.S. Pat. No. 4,086,743 issued to Hoopes on May 2, 1978; U.S. Pat. No. 4,101,029 issued to Feinberg et al. on Jul. 18, 1978; U.S. Pat. No. 4,161,247 issued to Feinberg et al. on Jul. 17, 1979; U.S. Pat. No. 4,165,770 issued to Goldman et al. on Aug. 28, 1979; and U.S. Pat. No. 4,372,095 issued to De Satnick on Feb. 8, 1983. Each of these patents are hereby expressly incorporated by reference in their entirety.

Many of the devices discussed in the above patents are either complex and inconvenient to employ or they are unsatisfactory in that they tend to damage the surface of the ball or otherwise adversely affect the ball's playing properties. Another significant drawback of the prior art is that such prior art contemplates pressurization of a very small number of tennis balls, typically, three tennis balls in a container of a configuration similar to the containers in which tennis balls are marketed.

The increasing popularity of tennis and the resultant growth in the offering of group tennis lessons, as well as the burgeoning tennis club industry, have resulted in the use of far more tennis balls than such prior art apparatus can economically preserve. For example, it is not uncommon for a tennis club in a large metropolitan area to use 10,000 or more tennis balls in a year. To address the large quantities of balls, some have proposed batch systems to re-pressurize balls. “Batch processing” typically refers to the processing of a plurality, for example 50 or more, tennis balls at one time. U.S. Pat. No. 4,101,029 issued to Feinberg et al. on Jul. 18, 1978, entitled Tennis Ball Rejuvenator and Maintainer and U.S. Pat. No. 4,046,491 issued to Roeder on Sep. 6, 1977, entitled Tennis Ball Preserver are examples of such batch systems.

Further complicating matters is that the ITF and/or national level sanctioning bodies have different ball specifications for different age groups of players. “Quick Start Tennis” is a program first introduced in 2007 to increase youth player participation for the game of tennis Quick Start Tennis incorporates smaller, lighter racquets and smaller courts sizes. Additionally, Quick Start Tennis incorporates three stages of tennis balls that have a lower rebound height than standard, adult tennis balls. Generally speaking, as players age from one “stage” to the next the balls they use play more closely to standard adult tennis balls. These tennis balls go by a variety of names which include Quick Start, 10 and Under Tennis, Play and Stay, etc. depending on the region of the world.

Beginning on Jan. 1, 2012 the ITF and other national sanctioning bodies modified the rules of tennis to require use the appropriate “Quick Start” tennis ball in all sanctioned events. Additionally, the ITF published specifications for size, mass, rebound height and forward deformation for each of the 3 stages in order for a ball to be ITF approved. Stage 3 balls have the lowest rebound height and are used for the youngest players. Stage 2 balls bounce slightly higher. Stage 1 balls bounce yet higher and are the closest to the standard adult tennis ball in terms of rebound height.

In light of the foregoing, there is a need for an improved apparatus and method for quickly recharging depressurized balls in an efficient and economical manner. The method and apparatus would also provide the ability to store them indefinitely. In addition, there is a need for an apparatus and method that is flexible enough to be used with multiple types and a varying number of pressurized balls, particularly tennis balls. Furthermore, there is a need for an apparatus and method that is flexible enough to recharge depressurized balls to different sets of specifications depending upon the particular sport.

SUMMARY OF THE INVENTION

The present invention is directed to an improved apparatus and method for quickly recharging a varying quantity of depleted pressurized balls in an efficient and economical manner.

In the method according to the invention a pressure vessel, specifically the hollow interior charging chamber of the pressure vessel, is filled with a plurality of discharged balls while the vessel is at ambient pressure. The pressure vessel is then sealed and the charging chamber is charged with a quantity of gas having a molecular weight heavier than air thereby increasing the internal pressure of the vessel. The internal pressure of the vessel is increased to a desired pressure and the balls are maintained within the chamber for a time sufficient to raise the internal pressure of the balls from an initial internal pressure to a desired internal pressure.

Another exemplary embodiment is a system for recharging depleted balls. The system includes a pressure vessel with a closed bottom and a spaced apart top with an integral, rigid wall extending between the closed bottom and top. The top may be selectively opened to permit access to the vessel's hollow interior charging chamber, which is sized to receive at least one ball.

The system also includes a gas port that is in at least selective fluid communication with the charging chamber of the pressure vessel. The gas port is suitable for connection to a pressurized gas supply where the gas has a molecular weight that is heavier than air. Preferably the system also includes a gas supply that is in at least selective fluid communication with the gas port and with the charging chamber.

The preceding system is sufficient to accomplish the goal of recharging depleted balls so that the depleted balls once again meet or come close to the bounce and other characteristics needed for appropriate play. It should also be noted that balls can be recharged in the system multiple times.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the following drawings, which form a part of the specification and which are to be construed in conjunction therewith, and in which like reference numerals have been employed throughout wherever possible to indicate like parts in the various views:

FIG. 1 is a schematic view of a recharging system in accordance with an exemplary embodiment of the invention;

FIG. 2 is a partially fragmented perspective view of a recharging vessel showing several tennis balls being recharged therein;

FIG. 3 is an elevational view of another exemplary embodiment of the invention taken generally from the side and with the opposite side being a mirror image thereof;

FIG. 4 is an elevational view of the embodiment of FIG. 3 with dashed lines showing movement;

FIG. 5 is a top plan view of the embodiment of FIG. 3;

FIG. 6 is an elevation view of the embodiment of FIG. 3 taken generally from the front side;

FIG. 7 is top view of an alternative embodiment of a recharging vessel.

FIG. 8 is an elevation view of the embodiment of FIG. 7 taken generally from the front side; and

FIG. 9 is an elevation view of the embodiment of FIG. 7 taken generally from the side and showing the top in an open position.

DETAILED DESCRIPTION OF THE INVENTION

The following paragraphs set forth exemplary descriptions of an apparatus and method according to the invention. As an aid to the reader, the description is in the context of recharging tennis balls but this narrative convenience should not be interpreted as limiting the scope of the invention, which is only limited by the claims. In the following description various mechanical elements are utilized which may vary in size and shape but perform the same function. In such instances the element numbers utilized to identify such elements are the same throughout the detailed description.

The phrase “discharged balls” as used herein generally means balls that no longer exhibit the pressurization suitable for play. More specifically, the phrase includes balls that no longer meet sanctioning body specifications for a particular sport. For tennis, such specifications would include the size of the ball, the internal pressure of a ball, the distance that balls must rebound when dropped from a standard height, the amount of deformation exhibited under an applied standard force, and/or their surface characteristics.

The term “recharged ball” as used herein means balls that have had their internal pressure increased from an initial pressure in accordance with the practice of the invention.

As shown in FIGS. 1 and 2 of the drawings, one exemplary embodiment of the present invention is generally designated by reference numeral 20. The present invention employs a pressure vessel 22 with a hollow internal charging chamber 24 that is essentially impermeable when sealed. The charging chamber 24 is formed from the hollow pressure vessel interior bounded between a closed end 26 and a spaced apart removable end or top 27 with a wall 28 extending therebetween. The removable top 27 may include the entire cylinder end as shown in FIG. 9 or a portion thereof as shown in FIG. 2.

In another exemplary embodiment shown in FIGS. 3-6, the pressure vessel 22 includes a removable end or top 27 that may be selectively opened to permit substantially unobstructed access to the interior charging chamber 24 defined by the bottom 26, top 27, and wall 28. The top 27 may be secured by several threaded bolts 41 equidistantly spaced about the vessel periphery. Alternatively, the top 27 may be secured by any other known means of securing tops to pressure vessels. Those skilled in the art will know how to adapt such means for use with the present invention. The top 27 may be pivotally secured to the vessel by an arm 40 that permits the top to open upwardly and swing outwardly from the vessel 22 as shown in FIG. 9. When the top 27 is open it is possible for the interior charging chamber of the pressure vessel to receive tennis balls that are to be recharged.

In the embodiments shown in the Figures, a gas charging port 29 penetrates vessel 22 proximate the selectively open top 27. The gas charging port 29 may be placed in the wall 28 of the pressure vessel 22 or it may be placed in the top 27 or bottom 26. The primary requirement for the gas charging port 29 is that it be in fluid communication with the hollow interior charging chamber 24 of the pressure vessel 22. The gas charging port 29 permits the entry and removal of gasses from the charging chamber 24. A pressure gauge 30 may penetrate vessel 22 adjacent port 29 or it may be placed at any desired and suitable position along the outer surface of the pressure vessel. Alternatively a removable pressure gauge may be placed on or connected to port 29 to thereby measure the internal pressure in chamber 24. The pressure vessel may also have a separate pressure relief valve for safety purposes.

One skilled in the art should realize that there are many different possible designs for a pressure vessel 22 that can be used in the practice of the invention.

Continuing with the embodiments shown in FIGS. 3-9, the top 27 is secured to the vessel 22 by the arm 40. The arm 40 includes a pivot 42 that permits the top 27 to swing upwardly to open and downwardly to close. A handle 45 mounted opposite the arm 40 facilitates user movement of the top 27. When closed, the top 27 is secured to the pressure vessel 22 using suitable means known to those skilled in the pressure vessel arts. In the embodiment shown in FIGS. 3-6 the securing means are bolts 41.

In the embodiment shown in FIGS. 3-6, the pressure vessel 22 is pivotally secured to a base 50 that permits the vessel to pivot in each direction relative to the base. The embodiment of the apparatus according to the invention that incorporates a base 50 is particularly well suited for very large pressure vessels that are designed to accept hundreds or thousands of balls at one time. Such vessels are generally too large and heavy for one person to easily handle thus a pivoting feature can greatly improve ease of use.

The base 50 has supporting arms 52 that each have a triangular outline although other shapes are possible so long as they provide a stable support for the pressure vessel 22 and permit its pivoting movement. The base 50 includes pivoting pins 55 (FIGS. 5 & 6) secured to the pressure vessel 22 and pivotally mounted to the base. The base 50 includes a flat floor 54 supporting the spaced apart and parallel arms 52 on the ground or other support surface. The arms 52 include a reinforcing gusset 53 spanning between the arms 52 that further stabilizes the arms 52 to maintain their spaced relationship.

A handle 60 secured to the vessel 22 and protruding outwardly facilitates pivoting movement by a user. In a preferred embodiment, the handle 60 is a component of a spring loaded locking mechanism comprising a spring 61 (FIG. 6) and a rotating wheel 62 (FIG. 3) having two or more spaced apart notches 63 along its perimeter that engage with the handle 60. When the pressure vessel 22 is in an upright position, the spring 61 places tension on the handle 60 facilitating engagement of the handle 60 with a notch 63 in the wheel 62 to secure the orientation of the pressure vessel 22. Pivoting of the pressure vessel 22 is accomplished by grasping the handle 60 and pulling the handle 60 out away from the vessel (against the tension of the spring 61) thereby disengaging the handle 60 from the notch 63 associated with upright positioning. The user may then pivot the vessel 22 in either direction. The degree of pivot can be established based on the preference of the user. Prototypes of the invention employed notches 63 at positions along the wheel allowing for 100° of rotation in each direction (i.e., 200° of total rotation). The amount of rotation may be adjusted by the user but 100° of rotation is recommended to facilitate easy removal of balls and movement of the vessel. Alternatively, the handle 60 and locking mechanism may be secured to another movement source for automated movement (e.g., an electric motor).

The invention may include a series of storage vessels 23 (FIG. 1) that are virtually identical to pressure vessel 22. The storage vessels may be appropriately plumbed to reuse gas released from the charging vessel 22 or they may be supplied with gas separately as appropriate. Such storage vessels may be used to store recharged balls at a desired pressure indefinitely. For example, tennis balls normally are stored between 17-22 psi (117-152 kPa) but could be stored at pressures anywhere from slightly above atmospheric to the limits of the pressure vessel.

Another embodiment of the invention is shown in FIGS. 7-9. This embodiment is similar to the embodiments shown in FIGS. 3-6. The primary difference between the two embodiments is that the pressure vessel 22 shown in FIGS. 7-9 does not pivot. Instead it is secured to a fixed base 72 and utilizes additional bolts 41 to secure the top 27.

It should be readily apparent to one skilled in the art that the size and shape of the pressure vessel utilized in the practice of the invention can vary to a large extent. For example, the embodiments shown in FIGS. 3-9 could be sized to handle a few hundred to a few thousand balls. Such large pressure vessels are commercially available.

Likewise, smaller pressure vessels capable of holding a few balls (e.g., 1-50) might be more suitable for the home or small tennis club environment. Such smaller pressure vessels are commercially available from pressure vessel suppliers and can be readily modified for use in accordance with the invention.

Both the pivoting and stationary embodiments of the apparatus according to the invention are connected to a compressed gas supply 70, schematically represented in FIG. 1. The gas supply 70 provides gas to the hollow interior charging chamber 24 of the pressure vessel 22 and thus must be in at least intermittent fluid communication with the gas port 29 and the charging chamber 24 of the pressure vessel 22. Preferably the gas supply 70 provides gas that has a molecular weight heavier than air (e.g., carbon dioxide) as discussed in more detail below.

Another benefit of the claimed system for recharging depleted tennis balls is the prevention of warping of recharged tennis balls. As noted in the background section above, other devices and methods for recharging depleted tennis balls are known. However, those that attempt to recharge balls using bulk, batch processes (i.e., batches that typically include 50 or more tennis balls) often have the problem of producing warped tennis balls. In other words, the tennis balls leaving the process have one or more flat spots on them, which make them unsuitable for further use as tennis balls.

At present it is believed that the warping is caused by at least two factors. First, the initial compression of the balls upon the application of increased pressure causes the outer diameter of the balls to shrink which allows them to pack more tightly in the initial phase of the recharge cycle. As they regain pressure they return to their full shape which forces some balls against the edge of the wall where they develop flat spots. Second, it is also believed that the weight of the balls becomes a factor when large numbers of balls are recharged. In other words, when large numbers of balls are recharged the balls at the bottom of a large recharging chamber are flattened by the weight of the balls above.

Early prototypes of the current invention also experienced this problem. In these early prototypes the problem was overcome by agitating the balls (e.g., shaking or pivoting the pressure vessel) at least once during the course of a recharging cycle. However, agitation adds another step to the recharging cycle so other means for preventing warping were explored. Accordingly, the system for recharging depleted tennis balls according to the invention also comprises various means for preventing warping of tennis balls during a recharging cycle.

One means of preventing warping of tennis balls in the system according to the invention is the previously described base 50 which pivotally supports the pressure vessel 22. Pivoting the pressure vessel (usually by about 45°) during a recharging cycle has been shown to eliminate warping. This means of preventing warping is particularly applicable to large recharging systems (i.e., those systems capable of handling 3000 or more balls) because it transfers a portion of the overall weight of the ball load to the sides of the vessel rather than placing all of the weight on the balls at the bottom of the vessel. In addition, pivoting the vessel greatly aids in the removal of balls from the vessel by simply dumping them out.

Another means of preventing warping of tennis balls in the system according to the invention was developed by noticing a relationship between the diameter of the early prototypes and the amount of warping. Two early prototypes were built. The first pressure vessel had a 9 inch (22.86 cm) diameter and 18 inch (45.72 cm) height. The second vessel had a 12 inch (30.48 cm) diameter and 24 inch (60.96) height. Both produced warped tennis balls. However, it was noticed that the degree of warping in the 12 inch (30.48 cm) diameter vessel was less than that seen in the 9 inch (22.86 cm) diameter vessel. Therefore a third prototype was built using a pressure vessel with a 20 inch (50.8 cm) diameter and a 36 inch (91.44 cm) height. The recharged balls from this prototype did not show signs of warping even when filled to capacity and in the absence of agitation. Thus there is a relationship between the height and diameter of the charging chamber of the pressure vessel and the degree of warping seen in recharged balls, at least for certain sized charging chambers. It is hypothesized that as the volume of the charging vessel increases the height to diameter ratio is not as critical for preventing warping as shown in the increase from the 18 inch:9 inch vessel to the 24 inch: 12 inch vessel.

Accordingly, one means of preventing warping in the claimed system for recharging tennis balls is to design the pressure vessel 22 such that its hollow interior charging chamber possesses a height sufficient and a diameter sufficient to allow the tennis balls to recharge without warping. Data to date indicates that a charging chamber having a height to diameter ratio less than 2.6:1, preferably less than 1.8:1, is sufficient to prevent warping of tennis balls during the practice of the invention. Thus, in preferred embodiments the charging chamber 24 utilized in the practice of the invention has a height to diameter ratio of less than 2.6:1. Particularly preferred embodiments of the invention utilize a ratio of less than 1.8:1.

However, as the size of the pressure vessel increases and the quantity of balls increases there comes a point where the shear weight of the balls overcomes the relationship between the diameter and height ratio and warping. In such instances pivoting or shaking the vessel to agitate the balls may be necessary to prevent warping. Those skilled in the art can optimize the design of the system to fit their particular needs vis-à-vis warping vs. quantity of balls per recharging cycle.

Balls recharged by the above-described system are also encompassed by the invention.

Turning now more toward the method according to the invention, of particular relevance to the present invention is Dalton's law. It says the total pressure of a gas is equal to the sum of the partial pressures of each of the component gases:

P _(total) =P ₁ +P ₂ +P ₃ . . . +P _(n)

If we consider air, this means the total atmospheric pressure of 1.013 bars (14.7 pounds per square inch absolute or 101 kPa) is the sum of the partial pressures of all its constituents: nitrogen, oxygen, water vapor, argon, carbon dioxide, and various other gases in trace amounts. In particular, air contains roughly 78% nitrogen, 21% oxygen, 0.93% argon, 0.04% carbon dioxide, and trace amounts of other gases, in addition to variable quantities of water vapor, which normally approximates 3%. The two most dominant components in dry air are Oxygen and Nitrogen. Oxygen has an atomic unit mass of 16 and Nitrogen has an atomic unit mass of 14. Since both of these elements are diatomic in air —O₂ and N₂, the molecular mass of Oxygen is 32 and the molecular mass of Nitrogen is 28. Since air is a mixture of gases the total mass can be estimated by adding the weight of all major components as shown below:

Volume Ratio Components in compared to Molecular Mass - Molecular Mass Dry Air Dry Air M (kg/kmol) in Air Oxygen 0.2095 32.00 6.704 Nitrogen 0.7809 28.02 21.88 Carbon Dioxide 0.0003 44.01 0.013 Hydrogen 0.0000005 2.02 0 Argon 0.00933 39.94 0.373 Neon 0.000018 20.18 0 Helium 0.000005 4.00 0 Krypton 0.000001 83.8 0 Xenon 0.09 10⁻⁶  131.29 0 Total Molecular Mass of dry Air 28.97 Water vapor H₂O is composed of one Oxygen atom and two Hydrogen atoms. Hydrogen is the lightest element at 1 atomic unit while Oxygen is 16 atomic units. Thus water vapor molecules have an atomic mass of 18 atomic units. At 18 atomic units, water vapor is lighter than diatomic Oxygen with 32 units and diatomic Nitrogen with 28 units. Thus, it is important to note that water vapor in air will replace other gases and reduce the total density of the mixture and hence dry air is more dense than humid air. Carbon dioxide (CO₂) on the other hand has an atomic mass of 44.01, which is more dense than dry air at 28.97.

Turning now to the steps associated with the method according to the invention, in broad terms the method according to the invention comprises the steps of (1) filling a pressure vessel charging chamber 24 by introducing a plurality of discharged balls into the charging chamber 24; (2) charging the charging chamber by sealing the chamber (e.g., closing the top 27) and then increasing the internal pressure of the chamber by introducing a quantity of gas with a molecular weight heavier than air, and (3) maintaining the balls within the chamber for a time sufficient for the balls to achieve a desired internal pressure. Typically the step of filling the chamber with balls will occur at ambient pressure due to the opening of the top 27 of the pressure vessel 22 at ambient conditions.

In preferred embodiments the gas having a molecular weight heavier than air is carbon dioxide. Other such gasses could be used in the practice of the invention but cost considerations and availability make carbon dioxide a preferred choice.

The step of filling a charging chamber 24 by introducing a plurality of balls 32 is carried out by opening the pressure vessel 22 and inserting discharged balls into the charging chamber 24. The introduction of multiple depleted tennis balls 32 introduces a quantity of air that is contained within the balls. In most instances the interior of the balls are at or near atmospheric pressure (i.e. air at approximately 14.7 psi or 101 kPa) or at least below a desired pressure. The total quantity of atmospheric air introduced by the balls is dependent upon the number of tennis balls introduced but can be expected to be the number of tennis balls multiplied by the internal volume of each ball, which can be calculated based upon the formula: sphere volume= 4/3·π·r³=(π·d³)/6. The acceptable measurements for the external diameter of tennis balls according to the International Tennis Federation is 2.575 inches (6.54 cm) to 2.700 inches (6.858 cm) with the outer covering and internal rubber core having a thickness of approximated 0.125 inches (0.3175 cm). Thus, the appropriate diameter is approximately 2.7 inches (6.86 cm) and the internal volume of each ball is approximately 8.17 cubic inches (133.882 cm³). Fifty such balls would have an internal volume of about 408.5 cubic inches (6694 cm³). The volume of the charging chamber of the pressure vessel volume is typically substantially larger.

The volume of a cylinder (i.e., the charging chamber) can be calculated using the formula: Volume=π·r²·height=¼·π·d²·height. In one early exemplary embodiment, the charging chamber 24 of a pressure vessel 22 has a radius of approximately 6 inches (15.24 cm) and a height of approximately 30 inches (76.2 cm). Thus, the volume of the charging chamber would be approximately 3391 cubic inches (i.e. 3.14×6²×30) or 55568 cm³. Such a charging chamber can hold 50 or more tennis balls. These dimensions can be scaled to create larger or smaller systems as needed. For example, a commercial model of the system according to the invention utilizing a pressure vessel approximately 6 feet (1.82 m) tall and 3 feet (0.91 m) in diameter can process around 5000 tennis balls per batch. Smaller systems using smaller, commercially available pressure vessels typically handle less than 50 balls. Those skilled in the art know the mathematical calculations necessary to design charging chambers of other sizes therefore they will not be demonstrated here.

In preferred embodiments, the charging chamber 24 utilized in the practice of the invention has a height sufficient and a diameter sufficient to allow the balls (e.g., tennis balls) to recharge under pressure without warping. In preferred embodiments such charging chambers 24 have a height to diameter ratio less than 2:1, preferably less than 1.8:1. Alternatively (or with larger vessels holding a substantial quantity/weight of balls) the method according to the invention can include a step of agitating the recharging balls at least once while they are recharging. The agitation can be accomplished by manually or mechanically jostling the pressure vessel (e.g., shaking a small vessel or pivoting a large one that rests on a base).

Introducing flat tennis balls 32 at atmospheric pressure into the charging chamber 24 does not change the pressure or gas concentrations inside the chamber, which are already at ambient room conditions. After the balls are added, the top 27 is closed or the chamber is otherwise sealed. The pressure in the charging chamber 24 is increased by introducing a quantity of pressurized gas having a molecular weight heavier than air (e.g., carbon dioxide). The gas is supplied by pressurized gas supply 70 attached to a gas port 29 as schematically represented in FIG. 1. The quantity of gas introduced is that which is sufficient to raise the internal pressure of a discharged ball from an initial internal pressure to a desired internal pressure. For adult tennis balls, a typical charging chamber pressure would be 60 psi. The pressure within the chamber can be adjusted up or down depending on cost, time, and safety factors. Generally speaking, and as discussed below, increasing the pressure will shorten the time needed for recharging while lowering the pressure will increase the time needed for recharging.

The added injected gas initially fills the charging chamber 24, increasing the pressure throughout the charging chamber. Each of the tennis balls 32 acts as a small pressure vessel with permeable walls that the pressurized gas must permeate over time. The internal pressure of each depleted tennis ball is usually around 14.7 psi (i.e. 1 atm) but over time the pressurized gas will penetrate the tennis ball 32 exterior as well as the semi-permeable rubber core or internal wall and begin equalizing the internal tennis ball pressure with the chamber internal pressure. As the chamber pressure decreases the pressure inside the balls will increase accordingly. For example, with tennis balls in a chamber initially pressurized to 60 psi, the internal pressures of the balls will rise from about 14 psi (96 kPa) to about 17 psi (117 kPa) while the chamber pressure will have decreased from 60 psi (413 kPa) to about 57 psi (393 kPa) over the course of about 3 days. Similarly, if the chamber pressure drops by 8 psi (55 kPa) the internal ball pressure should have increased to about 22 psi (152 kPa). Thus, it is possible to monitor the status of the charging tennis balls by monitoring the decreasing pressure of the charging chamber 24 over time via a pressure gage to determine when the balls are recharged.

It is also possible to monitor the amount of time that it takes an individual pressure vessel to recharge a number of balls. Since the invention may be practiced using multiple styles and shapes of pressure vessels the exact pressures and times used for one vessel may not be the optimum pressure and time for another vessel. Some vessels may have small leaks or the temperature of operation may change depending on where the vessel is located. Accordingly, those skilled in the art will recognize that for any particular vessel at any given pressure and temperature there will likely be a period of time that is optimum for recharging balls to a desired internal pressure. For example, over time, users will likely observe that for any particular system, “A”, recharging a number of balls, “B”, a recharge cycle at pressure, “C”, will require a time “D”. For such circumstances the practitioner will likely rely on time as the main factor for determining when to remove the balls. In most instances, it is preferable to use pressures that recharge balls in less than 10 days to maintain a sufficient supply of balls for daily use. While feasible to operate at lower pressures, it has been determined through experimentation that practicable time periods (i.e. less than 10 days) requires a chamber pressure of at least 40 psi (275 kPa) and more preferentially 60 psi (413 kPa) for recharging tennis balls.

It has been found that the number of tennis balls being recharged is not especially important in that 3 balls can be recharged in essentially the same time frame as 30 or more balls.

Once the pressure chamber 24 is pressurized to the desired pressure (i.e. 60 psi or 413 kPa), the balls may be subjected to an agitation step at some point in the process, preferably before the desired internal pressure is reached. For example, the pressure vessel 22 may be agitated to jostle the balls 32 inside the chamber. Alternatively, the pressure vessel 22 may be pivoted. It was found that pivoting large pressure vessels (such as a 6 foot tall (1.8 m) by 3 foot (0.91 m) diameter commercial prototype) by about 45 degrees during a recharging cycle prevents warping of the balls.

After the balls have achieved the desired internal pressure, the pressure in the charging chamber 22 is then reduced by releasing gas through gas port 29 or another suitable port until the pressure within the pressure chamber is at a desired level (e.g., the pressure gauge reads 14.7 psi if the vessel is to be opened or 17 psi if the balls are to be stored for a period of time). The balls are then removed from the chamber and used.

From the foregoing, it will be seen that this invention is well adapted to obtain all the ends and objects herein set forth, together with other advantages, which are inherent to the structure. It will also be understood that certain features and sub-combinations are of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and is within the scope of the claims. Many possible embodiments may be made of the invention without departing from the scope thereof. Therefore, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

Since other modifications and changes varied to fit particular operating requirements and environments will be apparent to those skilled in the art, the invention is not considered limited to the example chosen for purposes of disclosure, and covers all changes and modifications which do not constitute departures from the true spirit and scope of this invention. 

1. A system for recharging depleted balls, the system comprising: a pressure vessel with a closed bottom and a spaced apart, selectively open top with an integral rigid wall extending therebetween and having a charging chamber adapted to receive at least one ball to be recharged; and a gas port that is in fluid communication with the charging chamber wherein said gas port is suitable for connection to a pressurized gas supply, said gas having a molecular weight heavier than air.
 2. A system according to claim 1 further comprising a pressurized gas supply in at least selective fluid communication with the charging chamber wherein said gas has a molecular weight heavier than air.
 3. A system according to claim 1 further comprising a base pivotally supporting the pressure vessel, said base including at least two spaced apart arms, said arms pivotally secured to the vessel to permit pivotal movement of the vessel.
 4. A system according to claim 1 wherein said charging chamber has a height sufficient and a diameter sufficient to allow said balls to recharge without warping.
 5. A system according to claim 1 further comprising means for agitating said balls while they are within said pressure vessel.
 6. A system according to claim 1 wherein said pressure vessel further comprises a pressure gauge adapted to display vessel pressure.
 7. A system according to claim 1 wherein said charging chamber is capable of receiving a plurality of balls.
 8. A system according to claim 1 wherein said gas is carbon dioxide.
 9. A ball recharged by the system according to claim
 1. 10. A method of recharging depleted balls comprising the steps of: filling a pressure vessel charging chamber by introducing a plurality of discharged balls into the charging chamber; charging said chamber by sealing said chamber and then increasing the internal pressure of said chamber by introducing a quantity of gas with a molecular weight heavier than air; and maintaining said balls within said chamber for a time sufficient for said balls to achieve a desired internal pressure.
 11. The method of claim 10 further including the step of agitating the recharging balls at least once while recharging.
 12. The method of claim 10 wherein said charging chamber has a height sufficient and diameter sufficient to allow said balls to recharge under pressure without warping.
 13. The method of claim 10 wherein the gas is carbon dioxide.
 14. The method of claim 10 wherein the pressure within the pressure vessel charging chamber is sufficient to raise the internal pressure of a discharged ball.
 15. The method of claim 10 wherein the ball is a tennis ball.
 16. The method of claim 10 wherein said process is completed in less than 10 days.
 17. A method according to claim 10 further comprising reducing the pressure of said chamber after said balls achieve the desired internal pressure.
 18. A method according to claim 10 wherein the height to diameter ratio of the charging chamber is less than 2.6:1.
 19. A recharged ball produced in accordance with the process of claim
 10. 20. A ball according to claim 19 wherein said ball is a tennis ball. 